The idling governors customary nowadays, especially in diesel engines, control the idling speed of the engine with the use of a proportional controller, i.e., in the case of excessive or high idle speeds, less fuel is injected, resulting in torque reduction and, in the case of low idle speeds, more fuel is injected to increase the torque. On account of the differing frictional torques in a cold engine as opposed to a hot engine, and on account of a different torque delivery needed during idling for driving auxiliary units (for example the air conditioner), the idling speed changes, since a change in torque always entails a change in speed. Servo controls for use in conjunction with control units are known, which, for example in dependence on engine temperature, vary the feedback over the speed. This does not, however, result in a constant idling speed, especially since proportional controllers always exhibit certain control deviations. From the field of control technology it is known to eliminate these control deviations by imparting to the controller an integral-proportional behavior. With a closed control circuit, the integral portion of the controller resets the correcting variable unitl the actual speed is equal to the desired speed, i.e., the control deviation has been reduced to zero.
This solution per se, however, cannot be employed in an idling governor since the instantaneous speed during the driving operation is higher than the desired idling speed of the idling control circuit. If an integral controller were used, the result would be that the deviations from the idling speed would be constantly summed up, which, when reentering the idling control range, would effect an instantaneous setting to an idling speed which would be too low. This could result in stalling of the engine.